Different from the case for polar (0001) InxGa1-xN multiple quantum wells (MQWs), the effective radiative lifetimes (tau(R,eff)) at 8 K of violet (V: 3.15 eV), purple (P: 3.00 eV), and blue (B: 2.83 eV) emission peaks in nonpolar (1 (1) over bar 00) InxGa1-xN/GaN MQWs fabricated on various GaN templates were found to be nearly independent of InN molar fraction x being approximately 1 ns. The result indicates the absence of polarization fields parallel to the MQW normal. For each luminescence peak, the effective nonradiative lifetime (tau(NR),(eff)) at room temperature of the MQWs grown on "Ga-polar" wings of the GaN template prepared by lateral epitaxial overgrowth (LEO) was longer than that for the MQWs grown on "N-polar" Wings, windows, or on conventional GaN templates, which had high density basal plane stacking faults and threading dislocations. Since tau(R,eff) was little affected by the presence of defects, the increase in tau(NR,eff) brought fivefold improvement in the equivalent internal quantum efficiency (eta(eq)(int)) of V peak. Because B peak was mostly generated from defective areas, the increase in eta(eq)(int) was not so remarkable (29%-36%). However, these values are approximately twice that reported for (11 (2) over bar0) InGaN/GaN MQWs grown on LEO GaN templates [Onuma et al., Appl. Phys. Lett. 86, 151918 (2005)]. (C) 2007 American Vacuum Society.